This project is designed to understand the role of hormones (particularly T3 and prolactin) in normal mammary gland development and differentiation. We wish to understand how milk-protein production is controlled by various hormones. Studies include 1) Evaluation of the role of DNA synthesis in the response of tissue after explant culture in the presence of various hormones; 2) examination of the nature of the interaction of prolactin and human growth hormone with native as well as cryptic forms of lactogenic receptors; 3) to partially purify the lactogenic receptor in order to produce monoclonal antibodies against it; 4) purify alpha-lactalbumin from mouse mammary glands and prepare an antibody, and 5) examine the role of thyroid hormones in synthesis and secretion of milk proteins in organ culture.